1. Technical Field
This invention relates generally to seam tape, and more specifically relates to a seam tape having a longitudinally extending semi-rigid brace member formed of a plastic material, such as polyethylene, which reinforces the tape, and, hence, carpet seams, against buckling, and to the method of manufacturing such a seam tape.
2. Background Information
A longstanding problem in the carpet laying service is the tendency of adjoining carpets to rise along the length of their common seam. This unsightly buckling is caused by the stresses appearing at the seam, and is a source of frequent consumer complaints.
The most widely used means for attempting to retain the abutting carpet edges in a flat disposition is the well known heat bond seam tape. The tape is a composite structure of three primary elements. Essentially, an open mesh reinforcing means, or webbing, is held in sandwiched relation between a strip of paper and a strip of thermoplastic adhesive. The purpose of the tape is to secure the seam, i.e., to prevent the seam from separating responsive to oppositely directed stretching forces imparted to the abutting carpets. It is the weakness of the open mesh, or webbing, which allows the carpets to buckle, or lift, at the seam.
Another drawback of prior art hot melt seaming tape is the tendency for the webbing to separate from the paper upon which it is adhesively mounted when the heat seaming iron is used to melt the layer of thermoplastic adhesive. This phenomenon, known in the trade as web drag, severely weakens the tape and contributes to the lifting of the adjoining carpets at the seam.
One type of seam tape of the prior art is known as pin tape, and includes a plurality of metallic bracing members disposed in sandwiched relation to the paper base and the webbing. The braces have upstanding teeth with which to grab the carpet backing.
U.S. Pat. No. 4,935,280 discloses another prior art seaming tape having reinforcing filaments of high-strength yarn such as fiberglass, synthetic fibers or metal wire woven into the mesh backing of the tape. U.S. Pat. No. 4,565,728 discloses another type of seaming tape having metal wires embedded therein for heating in order to melt the adjacent adhesive, as well as reinforcing cords of fiberglass or the like. U.S. Pat. No. 4,416,713 shows another prior art carpet seaming tape which includes reinforcing filaments formed of rayon or glass fibers which extend transversely across the width of the tapes.
Although prior art carpet seaming tapes such as those discussed above all contain reinforcements, they are in fiber form. Although such fibers may provide reinforcing to the mesh, it does not provide the required reinforcement to prevent buckling or uplifting of the carpet edges at a seam.
U.S. Pat. No. 5,198,300 eliminates many of the problems discussed above with respect to prior art hot melt seaming tapes by the use of a plurality of longitudinally spaced, transversely extending metal brace members. Although this tape has been found to be satisfactory, it is relatively time consuming and difficult to manufacture, in that the metal brace members were difficult to apply and accurately position on the tape as it was being formed.
U.S. Pat. No. 5,691,051 eliminates many of these problems by providing a rigid strip of plastic acrylic material which reinforces the tape against buckling. However, one problem with this tape is that the plastic strip being formed of an acrylic material is rigid and somewhat brittle and could break easily and also is extremely difficult to form into rolled form for shipment and usage unless the tape is serrated along its length to permit it to be rolled into a roll form.
Another problem with existing seam tape is that the backing sheet which is usually formed of paper or other moisture absorbent material will collect mildew and mold especially when the overlying carpet is cleaned, which may provide a harmful condition to occupants of the house especially those suffering from allergies. Likewise, this paper backed tape is subject to deterioration and break down over time and also provides problems during manufacture since it will tear if an excessive pressure or tension is applied thereto.
Thus, there is a need in the carpet laying service for a seaming tape that provides lift-free seams. Furthermore, a need exists for an improved method in which such a carpet seaming tape can be mass produced relatively inexpensively, without sacrificing the advantages achieved by the tape when used in laying carpet, and which can be easily rolled into a roll form for convenience of storage, shipment and usage.